In Jujutsu you just rip the arm off; in fact, it could be half ripped off by the time he gets to the ground. In Aikido, you take them down and hold them in a controlled way from beginning to end - an altogether much harder task. At the end, you just sit there holding them. If your hold is good, and uke then tries to escape, then he will hurt or injure himself. To me, that's how it is.